[Yaffs] YAFFS checkins

[Charles Manning]

Hi YAFFSers

I have just checked in two sets of changes:

1) Linux: Allow use of vmalloc for large blockinfo data structure.
This was a problem because some people are using YAFFS with very large NAND 
arrays. This can cause the allocation of > 128kB - the limit of kmalloc for 
two data structures. Now YAFFS will try to use kmalloc but will use vmalloc 
if the kmalloc call fails.

2) YAFFS Direct: Improve the readdir and prefix handling.
There was a problem in the new speeded up readdir.
The previous prefix handling did not do a good job on prefixes that ended in a 
'/'. It would also match the first prefix in the config list that it could. 
Now it handles prefixes ending in '/' and searches for the longest matching 
prefix. You can now use nested prefixes.

-- CHarles